Sulfonic acid

Sulfonic acid

Sulfonic acid ester

Sulfonic

Sulfonic acids are organic sulfur compounds having the general structure R- SO2 -OH wherein R is an organic radical. Its salts and esters having the general structure R- SO2 -O- SO2 -O - R1 and -R2 hot sulfonates.

Sulfonic acids and their corresponding salts and esters, are classified into two groups: the aliphatic sulfonic acids or alkane sulfonic acids or sulfonates, and aromatic sulfonic acids and arene sulfonic acids or sulfonates.

Production and representation

For the technical preparation of the sulfonic acids, there are several synthetic routes, of which some examples are shown here.

A mixture of alkane sulfonic acids produced by the action of sulfur dioxide and oxygen at higher alkanes in the presence of radical initiators.

Aliphatic sulfonic acids can be synthesized by oxidation of thiols.

By nucleophilic substition the corresponding sulfonic acid salts are prepared from alkyl halides and sodium sulfite.

Arenesulfonic be produced by the sulfonation of aromatic compounds. There is an electrophilic aromatic substitution. The electrophilic reagent is sulfur trioxide in concentrated sulfuric acid in equilibrium.

Use and occurrence

Taurine is one of the few naturally occurring sulfonic acids as amino sulfonic acids. The sodium salts of sulfonic acids are often used as anionic surfactants in detergents. Of these, alkyl benzene sulfonates ( ABS) with the general formula CnH2n 1- C6H4- SO3 -Na was the most important representative until the 1960s the tetrapropylenebenzenesulfonate (TBS ). It had the soap largely replaced in the 1950s as a surfactant. However, it was found that TBS ( as many representatives of highly branched ABS) can be in the wastewater poorly degraded and it was therefore from 1964 through so-called linear alkylbenzene sulfonates (LAS ) replaced, which are the main surfactants in detergent chemistry for years. Practically, it is, however, less linear, but rather secondary alkyl benzene sulfonates. A linear alkyl benzene sulfonate is eg sodium dodecylbenzenesulfonate. Secondary alkyl sulfonic acid esters of phenol are used as plasticizers for PVC, PUR and rubber.

Tetrapropylenebenzenesulfonate (TBS )

Sodium dodecylbenzenesulfonate, example of the mixture of isomers.

Mesamoll softener

P-toluenesulphonic acid is an important reagent in organic synthesis.

A special application find polymers with sulfonate in water treatment, where they are used in ion exchangers for cations. Alkylbenzene sulfonates such as dodecylbenzene sulphonate are degraded in sewage treatment plants by microorganisms. Furthermore, sulfonic acids and their derivatives included in tannins and medicines. Also many dyes carrying sulfonate groups to obtain a high water solubility.

Properties

Alkanesulfonic acids are generally viscous liquids, said arenesulfonic acids form hygroscopic crystals. These dissolve easily in water and can be salted out by sodium chloride. Some sulfonic acids form stable, crystalline hydrates. Alkanesulfonic acids such as simple dieMethansulfonsäure are colorless liquids.

In contrast to the esters of sulfuric acid are R-S and not R -O -S bonds here. They also differ from the sulfones (R- SO2 - R '), which have no hydroxyl group. Sulfonic acids are stronger acids than carboxylic acids, because the sulfonic stronger electron-withdrawing effect on the hydroxy group carries as the carbonyl group, and the proton transfer is thus easier. Trifluoromethanesulfonic acid is even stronger than perchloric acid and thus belongs to the group of super acids.

Reactions

Nucleophilic Substitution

Arensulfonate can be converted at from 200 to 300 ° C by a nucleophilic substitution in amines, phenols, carboxylic acids or nitriles.

Salt formation

As mentioned above, sulfonic acids are strong acids like sulfuric acid, the salts formed with metal hydroxides. In contrast to the corresponding sulfates (salts of sulfuric acid), however, calcium - barium and lead (II) sulfonates dissolve well in water.

Desulfonylation of arenesulfonic

The sulfonation of aromatic compounds for the production of arenesulfonic acids is a reversible reaction. Specified in the preparation of benzene sulfonic acid is hydrolyzed, for example, at temperatures of 150 to 200 ° C with dilute hydrochloric acid to benzene: